如何使用 cmake 创建共享库?

2021-12-26 00:00:00 compilation shared-libraries cmake c++

我已经写了一个库，我曾经使用自己编写的 Makefile 进行编译，但现在我想切换到 cmake.树看起来像这样(我删除了所有不相关的文件):

<预><代码>.├── 包括│ ├── animation.h│ ├── buffers.h│ ├── ...│ ├── vertex.h│ └── world.h└── src├──动画.cpp├──缓冲区.cpp├── ...├── 顶点.cpp└── world.cpp

所以我想要做的只是将源代码编译成共享库，然后与头文件一起安装.

我发现的大多数示例都使用一些共享库编译可执行文件，但绝不仅仅是一个普通的共享库.如果有人能告诉我一个使用 cmake 的非常简单的库也会很有帮助，所以我可以以此为例.

解决方案

始终指定 cmake

的最低要求版本

cmake_minimum_required(VERSION 3.9)

您应该声明一个项目.cmake 说这是强制性的，它将定义方便的变量 PROJECT_NAME、PROJECT_VERSION 和 PROJECT_DESCRIPTION(后一个变量需要 cmake3.9):

project(mylib 版本 1.0.1 描述mylib 描述")

声明一个新的库目标.请避免使用file(GLOB ...).此功能不提供编译过程的有人参与的掌握.如果你懒惰，复制粘贴 ls -1 sources/*.cpp 的输出:

add_library(mylib 共享来源/动画.cpp源/缓冲区.cpp[...])

设置 VERSION 属性(可选，但这是一个好习惯):

set_target_properties(mylib PROPERTIES VERSION ${PROJECT_VERSION})

您还可以将SOVERSION 设置为VERSION 的主要编号.所以 libmylib.so.1 将是 libmylib.so.1.0.0 的符号链接.

set_target_properties(mylib PROPERTIES SOVERSION 1)

声明您的库的公共 API.将为第三方应用程序安装此 API.将它隔离在您的项目树中是一个很好的做法(比如将它放在 include/ 目录中).请注意，不应安装私有头文件，我强烈建议将它们与源文件放在一起.

set_target_properties(mylib PROPERTIES PUBLIC_HEADER include/mylib.h)

如果您使用子目录，则包含诸如 ../include/mylib.h" 之类的相对路径不是很方便.因此，在包含的目录中传递一个顶级目录:

target_include_directories(mylib PRIVATE .)

或

target_include_directories(mylib PRIVATE include)target_include_directories(mylib 私有源代码)

为您的库创建安装规则.我建议使用 GNUInstallDirs 中定义的变量 CMAKE_INSTALL_*DIR:

include(GNUInstallDirs)

并声明要安装的文件:

安装(目标 mylib图书馆目的地 ${CMAKE_INSTALL_LIBDIR}PUBLIC_HEADER 目的地 ${CMAKE_INSTALL_INCLUDEDIR})

您也可以导出 pkg-config 文件.此文件允许第三方应用程序轻松导入您的库:

  • 使用 Makefile，参见 pkg-config
  • 对于 Autotools，请参阅 PKG_CHECK_MODULES
  • 使用 cmake，请参阅 pkg_check_modules

创建一个名为 mylib.pc.in 的模板文件(参见 pc(5) 手册页了解更多信息):

prefix=@CMAKE_INSTALL_PREFIX@exec_prefix=@CMAKE_INSTALL_PREFIX@libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@includeir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@姓名:@PROJECT_NAME@描述:@PROJECT_DESCRIPTION@版本:@PROJECT_VERSION@要求:库:-L${libdir} -lmylibCflags: -I${includedir}

在你的 CMakeLists.txt 中，添加一个规则来扩展 @ 宏(@ONLY 要求 cmake 不扩展表单的变量${VAR}):

configure_file(mylib.pc.in mylib.pc @ONLY)

最后，安装生成的文件:

install(FILES ${CMAKE_BINARY_DIR}/mylib.pc DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/pkgconfig)

您也可以使用 cmake <代码>导出功能.不过这个功能只兼容cmake，我觉得很难用.

最后整个 CMakeLists.txt 应该看起来像:

cmake_minimum_required(VERSION 3.9)项目(mylib 版本 1.0.1 描述mylib 描述")包括(GNUInstallDirs)add_library(mylib 共享 src/mylib.c)set_target_properties(mylib 属性版本 ${PROJECT_VERSION}SOVERSION 1PUBLIC_HEADER api/mylib.h)配置文件(mylib.pc.in mylib.pc @ONLY)target_include_directories(mylib PRIVATE .)安装(目标 mylib图书馆目的地 ${CMAKE_INSTALL_LIBDIR}PUBLIC_HEADER 目的地 ${CMAKE_INSTALL_INCLUDEDIR})安装(文件 ${CMAKE_BINARY_DIR}/mylib.pc目的地 ${CMAKE_INSTALL_DATAROOTDIR}/pkgconfig)

编辑

正如评论中提到的，为了符合标准，您应该能够生成静态库和共享库.这个过程有点复杂，与最初的问题不符.但值得一提的是，它在这里有很好的解释.

I have written a library that I used to compile using a self-written Makefile, but now I want to switch to cmake. The tree looks like this (I removed all the irrelevant files):

.
├── include
│?? ├── animation.h
│?? ├── buffers.h
│?? ├── ...
│?? ├── vertex.h
│?? └── world.h
└── src
    ├── animation.cpp
    ├── buffers.cpp
    ├── ...
    ├── vertex.cpp
    └── world.cpp

So what I am trying to do is just to compile the source into a shared library and then install it with the header files.

Most examples that I have found compile executables with some shared libraries but never just a plain shared library. It would also be helpful if someone could just tell me a very simple library that uses cmake, so I can use this as an example.

解决方案

Always specify the minimum required version of cmake

cmake_minimum_required(VERSION 3.9)

You should declare a project. cmake says it is mandatory and it will define convenient variables PROJECT_NAME, PROJECT_VERSION and PROJECT_DESCRIPTION (this latter variable necessitate cmake 3.9):

project(mylib VERSION 1.0.1 DESCRIPTION "mylib description")

Declare a new library target. Please avoid the use of file(GLOB ...). This feature does not provide attended mastery of the compilation process. If you are lazy, copy-paste output of ls -1 sources/*.cpp :

add_library(mylib SHARED
    sources/animation.cpp
    sources/buffers.cpp
    [...]
)

Set VERSION property (optional but it is a good practice):

set_target_properties(mylib PROPERTIES VERSION ${PROJECT_VERSION})

You can also set SOVERSION to a major number of VERSION. So libmylib.so.1 will be a symlink to libmylib.so.1.0.0.

set_target_properties(mylib PROPERTIES SOVERSION 1)

Declare public API of your library. This API will be installed for the third-party application. It is a good practice to isolate it in your project tree (like placing it include/ directory). Notice that, private headers should not be installed and I strongly suggest to place them with the source files.

set_target_properties(mylib PROPERTIES PUBLIC_HEADER include/mylib.h)

If you work with subdirectories, it is not very convenient to include relative paths like "../include/mylib.h". So, pass a top directory in included directories:

target_include_directories(mylib PRIVATE .)

or

target_include_directories(mylib PRIVATE include)
target_include_directories(mylib PRIVATE src)

Create an install rule for your library. I suggest to use variables CMAKE_INSTALL_*DIR defined in GNUInstallDirs:

include(GNUInstallDirs)

And declare files to install:

install(TARGETS mylib
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
    PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})

You may also export a pkg-config file. This file allows a third-party application to easily import your library:

  • with Makefile, see pkg-config
  • with Autotools, see PKG_CHECK_MODULES
  • with cmake, see pkg_check_modules

Create a template file named mylib.pc.in (see pc(5) manpage for more information):

prefix=@CMAKE_INSTALL_PREFIX@
exec_prefix=@CMAKE_INSTALL_PREFIX@
libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@

Name: @PROJECT_NAME@
Description: @PROJECT_DESCRIPTION@
Version: @PROJECT_VERSION@

Requires:
Libs: -L${libdir} -lmylib
Cflags: -I${includedir}

In your CMakeLists.txt, add a rule to expand @ macros (@ONLY ask to cmake to not expand variables of the form ${VAR}):

configure_file(mylib.pc.in mylib.pc @ONLY)

And finally, install generated file:

install(FILES ${CMAKE_BINARY_DIR}/mylib.pc DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/pkgconfig)

You may also use cmake EXPORT feature. However, this feature is only compatible with cmake and I find it difficult to use.

Finally the entire CMakeLists.txt should looks like:

cmake_minimum_required(VERSION 3.9)
project(mylib VERSION 1.0.1 DESCRIPTION "mylib description")
include(GNUInstallDirs)
add_library(mylib SHARED src/mylib.c)
set_target_properties(mylib PROPERTIES
    VERSION ${PROJECT_VERSION}
    SOVERSION 1
    PUBLIC_HEADER api/mylib.h)
configure_file(mylib.pc.in mylib.pc @ONLY)
target_include_directories(mylib PRIVATE .)
install(TARGETS mylib
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
    PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
install(FILES ${CMAKE_BINARY_DIR}/mylib.pc
    DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/pkgconfig)

EDIT

As mentioned in comments, to comply with standards you should be able to generate a static library as well as a shared library. The process is bit more complex and does not match with the initial question. But it worths to mention that it is greatly explained here.

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